WASHINGTON — Massachusetts Gov. Deval Patrick says surveillance video from the Boston Marathon attack shows the suspect putting his backpack down and moving away in time to avoid being injured by the blast of the bomb inside it.

Speaking Sunday on NBC, Patrick says the video clearly puts 19-year-old Dzhokhar Tsarnaev (joh-KHAR' tsahr-NEYE'-ehv) at the scene of the attack. Tsarnaev is in serious condition at a Boston hospital after his capture Friday.

Patrick says the video is "pretty clear about his involvement and pretty chilling, frankly."

He says he hasn't viewed all the surveillance tapes but has been briefed by law enforcement about them.

Tsarnaev's older brother, Tamerlan, is also considered a suspect. He died in a gunbattle with police earlier Friday.

Investigators have determined the bombs were fashioned from pressure cookers packed with explosives, nails and ball bearings.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

The governor of Massachusetts said Sunday that he has no idea what motivated the brothers accused of exploding two bombs near the finish line of the Boston Marathon.

Speaking on CBS' "Face the Nation," Gov. Deval Patrick said it's hard to imagine why someone would deliberately harm "innocent men, women and children in the way that these two fellows did."

Patrick also said law enforcers believe the immediate threat ended when police killed one suspect and captured the other. The two suspects, Tamerlan and Dzhokhar Tsarnaev, were brothers whose family had come to the U.S. from Russia.

Tamerlan Tsarnaev, 26, was killed in a gunbattle with police Friday. Dzhokhar Tsarnaev, 19, was captured later Friday after being pulled bloody and wounded from a tarp-covered boat in a suburban Boston backyard. He is being guarded by armed officers while he recovers at a Boston hospital.

Three people were killed and more than 180 injured when two bombs, apparently fashioned out of pressure cookers, exploded Monday about four hours into the race. The brothers are also suspected of killing an MIT police officer and severely injuring a transit officer.

On Saturday, Patrick appeared on the field at Fenway Park with dozens of local and state police before the Boston Red Sox's first home game since the bombings. He said the hospitalized suspect was in serious but stable condition and wasn't able to communicate yet.